JSON for Modern C++ 3.8.0

accept
accept
accept
allocator_type
array
array_t
at
at
at
at
at
at
back
back
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
basic_json
begin
begin
binary
binary
binary
binary
binary_t
boolean_t
cbegin
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const_iterator
const_pointer
const_reference
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contains
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dump
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emplace_back
empty
end
end
erase
erase
erase
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error_handler_t
exception
find
find
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from_bson
from_bson
from_bson
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items
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json_sax_t
json_serializer
max_size
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number_float_t
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parser_callback_t
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sax_parse
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to_bson
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~basic_json
| ## ◆ sax_parse() [2/3] template<typename InputType , typename SAX >
static bool nlohmann::basic_json::sax_parse | ( | InputType && | i,
|  | SAX * | sax,
|  | input_format_t | format = `input_format_t::json`,
|  | const bool | strict = `true`
| ) |  |
| inline static
  The SAX event lister must follow the interface of json_sax. This function reads from a compatible input. Examples are: an std::istream object a FILE pointer a C-style array of characters a pointer to a null-terminated string of single byte characters an object obj for which begin(obj) and end(obj) produces a valid pair of iterators. Parameters
  [in] | i | input to read from
  [in,out] | sax | SAX event listener
  [in] | format | the format to parse (JSON, CBOR, MessagePack, or UBJSON)
  [in] | strict | whether the input has to be consumed completely
  Returns return value of the last processed SAX event Exceptions
  parse_error.101 | if a parse error occurs; example: `""unexpected end of input; expected string literal""`
  parse_error.102 | if to_unicode fails or surrogate error
  parse_error.103 | if to_unicode fails
  Complexity Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the SAX consumer sax has a super-linear complexity. Note A UTF-8 byte order mark is silently ignored. Example The example below demonstrates the `sax_parse()` function reading from string and processing the events with a user-defined SAX event consumer. 1 #include <iostream> 2 #include <iomanip> 3 #include <sstream> 4 #include <nlohmann/json.hpp> 5 6 using json = nlohmann::json; 7 8 // a simple event consumer that collects string representations of the passed 9 // values; not inheriting from json::json_sax_t is not required, but can 10 // help not to forget a required function 11 class sax_event_consumer : public json::json_sax_t 12 { 13 public: 14 std::vector<std::string> events; 15 16 bool null() override 17 { 18 events.push_back("value: null"); 19 return true; 20 } 21 22 bool boolean(bool val) override 23 { 24 events.push_back("value: " + std::string(val ? "true" : "false")); 25 return true; 26 } 27 28 bool number_integer(number_integer_t val) override 29 { 30 events.push_back("value: " + std::to_string(val)); 31 return true; 32 } 33 34 bool number_unsigned(number_unsigned_t val) override 35 { 36 events.push_back("value: " + std::to_string(val)); 37 return true; 38 } 39 40 bool number_float(number_float_t val, const string_t& s) override 41 { 42 events.push_back("value: " + s); 43 return true; 44 } 45 46 bool string(string_t& val) override 47 { 48 events.push_back("value: " + val); 49 return true; 50 } 51 52 bool start_object(std::size_t elements) override 53 { 54 events.push_back("start: object"); 55 return true; 56 } 57 58 bool end_object() override 59 { 60 events.push_back("end: object"); 61 return true; 62 } 63 64 bool start_array(std::size_t elements) override 65 { 66 events.push_back("start: array"); 67 return true; 68 } 69 70 bool end_array() override 71 { 72 events.push_back("end: array"); 73 return true; 74 } 75 76 bool key(string_t& val) override 77 { 78 events.push_back("key: " + val); 79 return true; 80 } 81 82 bool binary(json::binary_t& val) override 83 { 84 events.push_back("binary"); 85 return true; 86 } 87 88 bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override 89 { 90 events.push_back("error: " + std::string(ex.what())); 91 return false; 92 } 93 }; 94 95 int main() 96 { 97 // a JSON text 98 auto text = R"( 99 { 100 "Image": { 101 "Width": 800, 102 "Height": 600, 103 "Title": "View from 15th Floor", 104 "Thumbnail": { 105 "Url": "http://www.example.com/image/481989943", 106 "Height": 125, 107 "Width": 100 108 }, 109 "Animated" : false, 110 "IDs": [116, 943, 234, 38793], 111 "Distance": 12.723374634 112 } 113 } 114 )"; 115 116 // create a SAX event consumer object 117 sax_event_consumer sec; 118 119 // parse and serialize JSON 120 bool result = json::sax_parse(text, &sec); 121 122 // output the recorded events 123 for (auto& event : sec.events) 124 { 125 std::cout << "(" << event << ") "; 126 } 127 128 // output the result of sax_parse 129 std::cout << "\nresult: " << std::boolalpha << result << std::endl; 130 } Output (play with this example online):
      (start: object) (key: Image) (start: object) (key: Width) (value: 800) (key: Height) (value: 600) (key: Title) (value: View from 15th Floor) (key: Thumbnail) (start: object) (key: Url) (value: http://www.example.com/image/481989943) (key: Height) (value: 125) (key: Width) (value: 100) (end: object) (key: Animated) (value: false) (key: IDs) (start: array) (value: 116) (value: 943) (value: 234) (value: 38793) (end: array) (key: Distance) (value: 12.723374634) (end: object) (end: object)
      result: true
  The example code above can be translated with
      g++ -std=c++11 -Isingle_include doc/examples/sax_parse.cpp -o sax_parse
Since version 3.2.0 Definition at line 22529 of file json.hpp.

nlohmann::basic_json::number_unsigned_t
NumberUnsignedType number_unsigned_t
a type for a number (unsigned)
Definition: json.hpp:16548
nlohmann::basic_json::number_integer_t
NumberIntegerType number_integer_t
a type for a number (integer)
Definition: json.hpp:16477
nlohmann::basic_json::sax_parse
static bool sax_parse(InputType &&i, SAX *sax, input_format_t format=input_format_t::json, const bool strict=true)
generate SAX events
Definition: json.hpp:22529
nlohmann::basic_json::binary_t
nlohmann::byte_container_with_subtype< BinaryType > binary_t
a type for a packed binary type
Definition: json.hpp:16687
nlohmann::basic_json::json_sax_t
json_sax< basic_json > json_sax_t
SAX interface type, see nlohmann::json_sax.
Definition: json.hpp:16017
nlohmann::basic_json::string_t
StringType string_t
a type for a string
Definition: json.hpp:16379
nlohmann::basic_json::binary
static basic_json binary(const typename binary_t::container_type &init)
explicitly create a binary array (without subtype)
Definition: json.hpp:17456
nlohmann::basic_json::number_float_t
NumberFloatType number_float_t
a type for a number (floating-point)
Definition: json.hpp:16616
nlohmann::basic_json::parse_error
detail::parse_error parse_error
exception indicating a parse error
Definition: json.hpp:16030
nlohmann::basic_json::exception
detail::exception exception
general exception of the basic_json class
Definition: json.hpp:16028
nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2774